droidfish/DroidFish/jni/stockfish/movepick.h

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/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
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Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef MOVEPICK_H_INCLUDED
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#define MOVEPICK_H_INCLUDED
#include <algorithm> // For std::max
#include <cstring> // For std::memset
#include "movegen.h"
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#include "position.h"
#include "search.h"
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#include "types.h"
/// The Stats struct stores moves statistics. According to the template parameter
/// the class can store History, Gains and Countermoves. History records how often
/// different moves have been successful or unsuccessful during the current search
/// and is used for reduction and move ordering decisions. Gains records the move's
/// best evaluation gain from one ply to the next and is used for pruning decisions.
/// Countermoves store the move that refute a previous one. Entries are stored
/// using only the moving piece and destination square, hence two moves with
/// different origin but same destination and piece will be considered identical.
template<bool Gain, typename T>
struct Stats {
static const Value Max = Value(2000);
const T* operator[](Piece pc) const { return table[pc]; }
void clear() { std::memset(table, 0, sizeof(table)); }
void update(Piece pc, Square to, Move m) {
if (m == table[pc][to].first)
return;
table[pc][to].second = table[pc][to].first;
table[pc][to].first = m;
}
void update(Piece pc, Square to, Value v) {
if (Gain)
table[pc][to] = std::max(v, table[pc][to] - 1);
else if (abs(table[pc][to] + v) < Max)
table[pc][to] += v;
}
private:
T table[PIECE_NB][SQUARE_NB];
};
typedef Stats< true, Value> GainsStats;
typedef Stats<false, Value> HistoryStats;
typedef Stats<false, std::pair<Move, Move> > MovesStats;
/// MovePicker class is used to pick one pseudo legal move at a time from the
/// current position. The most important method is next_move(), which returns a
/// new pseudo legal move each time it is called, until there are no moves left,
/// when MOVE_NONE is returned. In order to improve the efficiency of the alpha
/// beta algorithm, MovePicker attempts to return the moves which are most likely
/// to get a cut-off first.
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class MovePicker {
MovePicker& operator=(const MovePicker&); // Silence a warning under MSVC
public:
MovePicker(const Position&, Move, Depth, const HistoryStats&, Square);
MovePicker(const Position&, Move, const HistoryStats&, PieceType);
MovePicker(const Position&, Move, Depth, const HistoryStats&, Move*, Move*, Search::Stack*);
template<bool SpNode> Move next_move();
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private:
template<GenType> void score();
void generate_next_stage();
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const Position& pos;
const HistoryStats& history;
Search::Stack* ss;
Move* countermoves;
Move* followupmoves;
Depth depth;
Move ttMove;
ExtMove killers[6];
Square recaptureSquare;
Value captureThreshold;
int stage;
ExtMove *cur, *end, *endQuiets, *endBadCaptures;
ExtMove moves[MAX_MOVES];
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};
#endif // #ifndef MOVEPICK_H_INCLUDED